Active porous transition towards spatiotemporal control of molecular flow in a crystal membrane.

Takasaki Y, Takamizawa S - Nat Commun (2015)

Bottom Line:
Fluidic control is an essential technology widely found in processes such as flood control in land irrigation and cell metabolism in biological tissues.In any fluidic control system, valve function is the key mechanism used to actively regulate flow and miniaturization of fluidic regulation with precise workability will be particularly vital in the development of microfluidic control.Here we show that the introduction of a stress-induced martensitic transition mechanism converts a microporous molecular crystal into an active fluidic device with spatiotemporal molecular flow controllability through mechanical reorientation of subnanometre channels.

ABSTRACTFluidic control is an essential technology widely found in processes such as flood control in land irrigation and cell metabolism in biological tissues. In any fluidic control system, valve function is the key mechanism used to actively regulate flow and miniaturization of fluidic regulation with precise workability will be particularly vital in the development of microfluidic control. The concept of crystal engineering is alternative to processing technology in microstructure construction, as the ultimate microfluidic devices must provide molecular level control. Consequently, microporous crystals can instantly be converted to microfluidic devices if introduced in an active transformability of porous structure and geometry. Here we show that the introduction of a stress-induced martensitic transition mechanism converts a microporous molecular crystal into an active fluidic device with spatiotemporal molecular flow controllability through mechanical reorientation of subnanometre channels.

f2: Active positional controllability of martensitic transition.(a) Growth of 5-μm-wide band from the pushed edge of the (1-1-1) crystal surface at room temperature. (b) Connection of mother (α phase) and daughter (α' phase) crystals at 298 K accompanied by the rotation of channel direction (green bands) under the twinned state with a bending angle of 14.6° along the projected direction of [010]α and [010]α' based on crystallography. (c) Schematic explanation for the regulation of the α' crystal domains sandwiched by the pushing positions as a shear on {1-1-1}α. (d) Picture of an experimental system. (e) Active generation/degeneration of daughter crystal domains by shearing the microcrystal of 1 (0.48 × 0.17 × 0.10 mm) with movable needles (f) and figures indicating the directions of the penetrating channels. (Inset pictures in e: highlighted α' domains by reflecting light due to the parallel crystal surfaces in each crystal phase.; see Supplementary Movie 1 for e).

Mentions:
We accidentally found stress-induced martensitic transition behaviour on a microporous single-crystal host, [Cu(II)2(bza)4(pyz)]n (bza: benzoate; pyz: pyrazine) (1), which can be a microfluidic crystal for gaseous fluid (Fig. 1). By pushing the crystal surface (00-1) of 1 with a glass needle at room temperature, while one edge of the crystal is fixed to a base, a stress-induced daughter phase began to grow out from {1-1-1} with an unchanging bandwidth of about 5 μm sandwiched by two parallel planar interfaces. The edge of the band ran 133 μm ms−1 along [010] direction (Fig. 2a). After going across the crystal, the thin band broadened in 0.5 μm ms−1 to separate the interfaces (Supplementary Fig. 1). The daughter domain spontaneously contracted and disappeared by removal of the stress through the reverse transition with organosuperelasticity1516, which simplifies the reverse operation. This is the first example of a superelastic crystal consisting of metal complexes. Crystal phase indexing under the coexisting state of the mother (α) and daughter (α′) phases revealed a rotation twin in which the crystal lattice was maintained but was rotated accompanied by the rotation of channel direction in rearranging 0.8-nm-width pore units during the structural phase transition on the boundary (Fig. 2b, Supplementary Figs 2–4 and Supplementary Table 1). The channels in the α and α′ phases run in a skewed position in the twinned crystal, which is slightly bent at the phase boundary by 14.6° along the projected direction of [010]α and [010]α′, as seen in Fig. 2b. Thus, the generation of the α′ phase can change the direction of gas permeation by mechanical twinning and the width or number of channels in the generated α′ domains are precisely regulated by the shear range of the mother α crystal, as shown in Fig. 2c–f and Supplementary Fig. 5.

f2: Active positional controllability of martensitic transition.(a) Growth of 5-μm-wide band from the pushed edge of the (1-1-1) crystal surface at room temperature. (b) Connection of mother (α phase) and daughter (α' phase) crystals at 298 K accompanied by the rotation of channel direction (green bands) under the twinned state with a bending angle of 14.6° along the projected direction of [010]α and [010]α' based on crystallography. (c) Schematic explanation for the regulation of the α' crystal domains sandwiched by the pushing positions as a shear on {1-1-1}α. (d) Picture of an experimental system. (e) Active generation/degeneration of daughter crystal domains by shearing the microcrystal of 1 (0.48 × 0.17 × 0.10 mm) with movable needles (f) and figures indicating the directions of the penetrating channels. (Inset pictures in e: highlighted α' domains by reflecting light due to the parallel crystal surfaces in each crystal phase.; see Supplementary Movie 1 for e).

Mentions:
We accidentally found stress-induced martensitic transition behaviour on a microporous single-crystal host, [Cu(II)2(bza)4(pyz)]n (bza: benzoate; pyz: pyrazine) (1), which can be a microfluidic crystal for gaseous fluid (Fig. 1). By pushing the crystal surface (00-1) of 1 with a glass needle at room temperature, while one edge of the crystal is fixed to a base, a stress-induced daughter phase began to grow out from {1-1-1} with an unchanging bandwidth of about 5 μm sandwiched by two parallel planar interfaces. The edge of the band ran 133 μm ms−1 along [010] direction (Fig. 2a). After going across the crystal, the thin band broadened in 0.5 μm ms−1 to separate the interfaces (Supplementary Fig. 1). The daughter domain spontaneously contracted and disappeared by removal of the stress through the reverse transition with organosuperelasticity1516, which simplifies the reverse operation. This is the first example of a superelastic crystal consisting of metal complexes. Crystal phase indexing under the coexisting state of the mother (α) and daughter (α′) phases revealed a rotation twin in which the crystal lattice was maintained but was rotated accompanied by the rotation of channel direction in rearranging 0.8-nm-width pore units during the structural phase transition on the boundary (Fig. 2b, Supplementary Figs 2–4 and Supplementary Table 1). The channels in the α and α′ phases run in a skewed position in the twinned crystal, which is slightly bent at the phase boundary by 14.6° along the projected direction of [010]α and [010]α′, as seen in Fig. 2b. Thus, the generation of the α′ phase can change the direction of gas permeation by mechanical twinning and the width or number of channels in the generated α′ domains are precisely regulated by the shear range of the mother α crystal, as shown in Fig. 2c–f and Supplementary Fig. 5.

Bottom Line:
Fluidic control is an essential technology widely found in processes such as flood control in land irrigation and cell metabolism in biological tissues.In any fluidic control system, valve function is the key mechanism used to actively regulate flow and miniaturization of fluidic regulation with precise workability will be particularly vital in the development of microfluidic control.Here we show that the introduction of a stress-induced martensitic transition mechanism converts a microporous molecular crystal into an active fluidic device with spatiotemporal molecular flow controllability through mechanical reorientation of subnanometre channels.

ABSTRACTFluidic control is an essential technology widely found in processes such as flood control in land irrigation and cell metabolism in biological tissues. In any fluidic control system, valve function is the key mechanism used to actively regulate flow and miniaturization of fluidic regulation with precise workability will be particularly vital in the development of microfluidic control. The concept of crystal engineering is alternative to processing technology in microstructure construction, as the ultimate microfluidic devices must provide molecular level control. Consequently, microporous crystals can instantly be converted to microfluidic devices if introduced in an active transformability of porous structure and geometry. Here we show that the introduction of a stress-induced martensitic transition mechanism converts a microporous molecular crystal into an active fluidic device with spatiotemporal molecular flow controllability through mechanical reorientation of subnanometre channels.